In a mobile communication network, such as a CDMA communication network or an LTE (Long Term Evolution) communication network, a plurality of radio base stations configure radio communication areas, respectively. Each of the base stations transmits a reference signal encoded by using a code assigned to each of the base stations (see JP11-308655A). A mobile device decodes the reference signal received from each of the plurality of base stations and identifies each of the base stations by identifying the code of the reference signal.
The number of the codes used by the base stations to encode the reference signal is limited, and the codes are reused in the mobile communication network. For this reason, there is a case where a plurality of base stations using the same code exist among the base stations included in the mobile communication network.
Usually, the code of each of the base stations is determined automatically or manually so as to prevent the radio communication areas of the base stations that use the same code from overlapping with each other. However, since the radio communication areas complicatedly overlap with each other, there is a high possibility that the radio communication areas of the base stations that use the same code will overlap with each other in a part of the areas. Further, there is also a possibility that the radio communication areas of the base stations that use the same code will overlap with each other due to human error.
Here, for example, a case is considered in which each of two base stations A and B that respectively configure radio communication areas adjacent to each other transmits a reference signal by using the same code. In this case, even when a mobile device moves from the radio communication area of base station A to the radio communication area of base station B, the code of the reference signal having the highest reception intensity is not changed. For this reason, the mobile device cannot recognize that it has moved from the radio communication area of base station A to the radio communication area of base station B. As a result, the mobile device is disposed to continue communication with base station A.
However, since the mobile device has actually moved into the radio communication area of base station B, the quality of communication with base station A has deteriorated, so that communication with base station A is disconnected. Here, assume that the phenomenon that causes communication disconnection to be generated in this way will be referred to as “collision” of a code of a radio reference signal.
In order to detect the collision of the code of the radio reference signal, work is performed in which, while an automobile, or the like, loaded with measuring instrument moves in the radio communication areas, reference signals transmitted from a plurality of base stations and received at measurement points are measured by using the measuring instrument, and in which the reference signal with the highest reception intensity is recorded for each of the measurement points. Then, “the collision of the code of the radio reference signal” is detected in such a manner that, on the basis of the recorded information, the position and shape of the radio communication area of each of the base stations on the map are recognized and formed into an image so as to be viewed by a person.